Magnetic conductors of electric machines provide low magnetic reluctance when magnetic fluxes pass therethough. The magnetic fluxes are created by sources of magnetic field, specifically, an electromagnet coil and a permanent magnet. When the magnetic flux is conduct through the magnetic conductors, occurring losses define efficiency of an electrical machine.
A first group of losses is determined by and a configuration of magnetic conductor and a material from which the aforesaid magnetic conductor is made. These loses are heat generation when a slowly varying is conducted by the magnetic conductor. The losses are caused by eddy-currents (Foucault currents) and hysteresis losses (magnetic reversal). Herewith, a material of magnetic conductor should be characterized by high saturation magnetic induction.
To reduce eddy-current losses, the magnetic conductor is made of non-conductive material. For example, the magnetic conductor is stacked of steel stampings coated with non-conductive organosilicon polymers. The stampings are oriented in a certain manner relative to the magnetic flux which is conducted through the magnetic conductor. An alternative technical solution is a powdery ferromagnetic material comprising an isolating filling compound.
The hysteresis losses are reduced by use of materials characterized by a narrow hysteresis loop and high value of magnetic permeability. In the case of a magnetic conductor made of an anisotropic material, minimal losses appear along a direction of easy magnetization.
However, a classical arrangement of an electrical machine comprises a magnetic conductor made of rolled steel to which the magnets are connected. Referring to FIG. 8, a stator plate 180 of 4-pole electric machine cut from steel sheet laminated by organosilicon polymers. As seen in FIG. 8, only a portion of a magnetic flux Φ is parallel to a direction of easy magnetization.
Use of isotropic material is limited by technical problems with producing magnetic conductors of large dimension and complex configuration which link sources of magnetic field in the electric machine.
A second group of losses is attributed to the electrical machine with permanent magnets.
The permanent magnets are demagnetized under influence of magnetic fluxes of the electromagnets. The aforesaid demagnetization results in depression of magnetic flux and, correspondingly, decrease in rotational torque and power.
Additionally, in the electrical machines with permanent magnets, a cogging torque ripple makes starting of the electrical machine from rest difficult and slows it down at work. The permanent magnets are in an effort to be in position corresponding to minimal reluctance of a closed path of magnetic flux.
In accordance with the abovementioned discussion, reduction of losses of the first and second groups is a long-felt and unmet need which is relevant to both electric-power production by an electrical generator and electric energy consumption by an electrical motor. Specifically, as to the electrical machine with permanent magnets, a long-felt need is to prevent the aforesaid permanent magnets from demagnetization and reduce cogging torque ripple.